In advanced microelectronic chips, that structure referred to as back-end-of-line (BEOL) metallization requires several layers of metal interconnections that are separated by a dielectric. Presently, the dielectric typically employed is fabricated of sputtered quartz which has a dielectric constant of about 3.9. However, in order to reduce signal delays in future chips, it will become necessary to reduce the dielectric constant of the insulator so that the capacitance between metal levels will be reduced. Much effort is now involved in attempting to replace the quartz with various polyimides. Polyimides generally have a dielectric constant of at least about 2.8 and are deposited onto the chip by wet spin-on techniques followed by subsequent drying at elevated temperatures. However, wet-processing, spin-on and drying techniques are undesirable from a standpoint of reproduceability and from an environmental viewpoint in view of the volatile organic solvents required.
Halogenated polymeric materials such as poly(tetrafluoroethylene) (PTFE) are attractive candidates for advanced electronic packaging applications because of their very low dielectric constants, excellent chemical stability, low solvents/moisture absorption and excellent thermal stability. However, because of their relative chemical inertness and hydrophobic nature, these halogenated polymeric materials are difficult to process into electronic packaging structures. The lack of effective processing techniques has inhibited the exploitation of these materials by the electronics industry. The low surface energy of these materials gives the inability to adhere to other surfaces and must be effectively overcome to yield desirable metal adhesion for practical electronic packaging applications.
More recently, as described in copending U.S. patent application Ser. No. 07/693,736 and now U.S. Pat. No. 5,244,730, (DOCKET NO. YO989-053) filed concurrently herewith, disclosure of which is incorporated herein by reference, a plasma enhanced chemical vapor deposition technique has been provided for the fabrication of polymeric fluorocarbon films that can be used as interlevel insulator between metal line interconnects in integrated circuits. However, even with this new advanced technique, adhesion to various substrates is still not entirely satisfactory.